You are here
Status of Spring
How do you know when spring has begun? Is it the appearance of the first tiny leaves on the trees, or the first crocus plants peeping through the snow? The First Leaf and First Bloom Indices are synthetic measures of these early season events in plants, based on recent temperature conditions. These models allow us to track the progression of spring onset across the country.
How does this spring compare to "normal"?
July 1st, 2019
Spring leaf out is complete across the Continental U.S. and Alaska. In the west, spring leaf out was 1-2 weeks early in parts of California and Nevada, and 2-3 weeks late in much of Oregon and Washington. In the east, spring leaf out was 1-2 weeks early in the upper Southeast, and 1-2 weeks late across the Great Plains, Midwest and parts of the Northeast.
Spring bloom arrived on time to 2 weeks early in much of the South, Appalachian Mountains, and mid-Atlantic. Parts of the low elevation West, Southern Great Plains, and much of the Northern Great Plains, Midwest, and Upper Northeast were 1-2 weeks late.
How often do we see springs this early or late for these locations?
Darker colors on the maps at right represent spring leaf out and bloom that are unusually early or late in the long-term record for that location. Gray indicates an average spring.
When did spring arrive at locations across the country?
The First Leaf Index map at right shows locations that have reached the requirements for the Spring Leaf Index model so far this year.
The First Bloom Index map at right shows locations that have reached the requirements for the First Bloom Index model.
Learn more about the Extended Spring Indices and the data products available.
USA-NPN also produces a suite of Accumulated Growing Degree Day map products.
What is behind these maps?
The Extended Spring Indices are mathematical models that predict the "start of spring" (timing of leaf out or bloom for species active in early spring) at a particular location (Schwartz 1997, Schwartz et al. 2006, Schwartz et al. 2013). These models were constructed using historical observations of the timing of first leaf and first bloom in a cloned lilac cultivar (S. x chinensis 'Red Rothomagensis') and two cloned honeysuckle cultivars (Lonicera tatarica 'Arnold Red' and L. korolkowii 'Zabelii').
Primary inputs to the model are temperature and weather events, beginning January 1 of each year (Ault et al. 2015). Maps are based on temperature products from NOAA National Centers for Environmental Prediction Real-Time Mesoscale Analysis. More information in our Gridded Product Documentation.
To calculate how often we see a spring like the current year, for each pixel, the 2019 Spring Index Anomaly value is compared to the anomaly value for each year from 1981-2018 (a 38 year record). We determine how often a spring was at least this early (or late) by taking the 38 years in the record divided by the count of years that were earlier (or later) than 2019.
Re-use of Maps and Data
Content, maps, and data accessible via usanpn.org are openly and universally available to all users. USA-NPN is not responsible for the content or the use of the data. Content may be re-used and modified with appropriate attribution (e.g., "source: USA National Phenology Network, www.usanpn.org"). See our complete Content Policy and Data Use Policy.